严重急性呼吸综合征康复病例血清中和抗体三年追踪观察

目的了解严重急性呼吸综合征（SARS）康复病例病后3年血清中和抗体水平及其变化规律,为SARS疫苗的研制和使用决策提供理论依据。方法对SARS康复病例进行随访,分别采集病后第5个月、第20个月和第35个月的血清,每份血清标本均采用间接酶联免疫吸附试验（ELISA）和微量中和试验二种方法进行血清SARS-CoV特异性抗体的检测。中和抗体效价采用Reed-Muench方法计算。3个时间点中和抗体效价的趋势分析采用对数转换后的数据进行重复测量方差分析。结果分别采集到病后第5个月、第20个月和第35个月的血清标本13份、17份和13份,采用ELISA法检测的抗体阳性率分别为100%、82．4%和84．6%,而采用中和试验法检测的中和抗体阳性率均为100%,中和抗体效价依次为1：43（1：16～1：203）、1：36（1：17～1：59）和1：21（1：10～1：39）,其差异具有统计学意义（F=60．419,P＜0．001）。病后第35个月时有30．8%（4/13）的病例血清中和抗体效价高于1：36,但另有30．8%（4/13）的病例血清中和抗体效价等于或略高于1：10（临界水平1：8）。结论SARS病例血清中和抗体至少可持续3年,但中和抗体效价随康复时间延长呈逐渐下降趋势;血清中和抗体效价个体差异较大,病后第35个月时部分病例的血清中和抗体效价已降至较低水平,何时完全消失尚需进一步追踪观察。

A three-year follow-up study on sera specific antibody in severe acute respiratory syndrome cases after the onset of illness

OBJECTIVE: To study the variation of specific antibody among convalescent of severe acute respiratory syndrome (SARS) patients through a three-year program. METHODS: Sera samples were collected from SARS cases in the 5th, 20th and 35th month after onset of the illness. The SARS-CoV specific antibody was detected for all of them by ELISA and neutralized test simultaneously. The titer of neutralizing antibodies was calculated using Reed-Muench method, and the comparison between different time groups was analyzed regarding the variance of data on repeated measures after logarithm conversion. RESULTS: 13, 17 and 13 sera samples were collected in the 5th, 20th and 35th month after onset. Results showed that despite the fact that the positive rates of ELISA antibody were 100%, 82.4% and 84.6% respectively,the neutralizing antibody was still positive for all the samples. The average neutralizing antibody titers were 1:43 (1:16-1:203), 1:36 (1:17-1:59) and 1:21 (1:10-1:39) on the 5th, 20th and 35th month after onset, and the differences were statistically significant (F = 60.419, P < 0.001). On the 35th month after the onset, 30.8% (4/13) of the patients were still having the neutralizing antibody level of above 1:36, but the neutralizing antibody level in another 30.8% (4/13) of the patients had decreased to as low as 1:10, when the cut-off level was set as 1:8. CONCLUSION: Results of the study indicated that the neutralizing antibody of SARS cases could last for at least three years, but the sera specific antibody in SARS cases decreased gradually when time went by. However, neutralizing antibody in some of the cases decreased to a lower level on the 35th month. Further follow-up study was worthwhile to observe the long-lasting profile of antibody existence on SARS cases.